Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating Activities
Net income	$ 27,949	$ 23,706
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation and amortization	3,764	3,829
Stock-based compensation	1,965	1,276
Loss (gain) on disposal of property, plant and equipment	258	(105)
Changes in operating assets and liabilities:
Accounts receivable	(123,249)	(108,939)
Inventories	(1,563)	(2,556)
Prepaid expenses and other assets	2,304	(1,577)
Accounts payable	2,876	(666)
Accrued expenses and other liabilities	(13,939)	(11,327)
Income taxes receivable/payable	13,191	12,239
Net cash used in operating activities	(86,444)	(84,120)
Investing Activities
Expenditures for property, plant and equipment	(4,312)	(2,439)
Proceeds from sales of property, plant and equipment		4,249
Net cash (used in) provided by investing activities	(4,312)	1,810
Financing Activities
Borrowings under line of credit	93,000	148,500
Principal payments under line of credit	(16,000)	(14,000)
Repurchases of common stock	(3,244)	(53,968)
Financing costs		(485)
Proceeds from employee stock purchase and option plans	103	72
Net cash provided by financing activities	73,859	80,119
Net decrease in cash and cash equivalents	(16,897)	(2,191)
Cash and cash equivalents, beginning of period	18,664	5,995
Cash and cash equivalents, end of period	1,767	3,804
Supplemental Disclosure:
Cash paid for interest	64	248
Cash paid for income taxes, net	$ 556	$ 498